1. Field of the Invention
The present invention relates to a sheet or film-forming roll, and more particularly, relates to touch rolls suitable for forming of a thin sheet or film.
2. Description of the Related Art
There has been known a touch-roll type sheet or film-forming method for successively forming a sheet or film by supplying melting resin from a T-shaped die in an interval between a main roll and a sub roll (touch roll).
Japanese Patent Publication Laid-open No. 2002-36332 discloses a touch roll having a double structure of an outer cylinder and an inner cylinder. In the touch roll, the outer cylinder is formed with a thin-walled structure of metal, while a crowning is applied on an outer profile of the touch roll.
While, Japanese Patent Publication No. 3194904 discloses another touch roll having a double structure of an outer cylinder and an inner cylinder. In this touch roll, the outer cylinder is formed with a thin-walled structure of metal. Additionally, the outer cylinder is elastically deformed while following an outer circumferential surface of the main roll by an imposed load against the main roll.
Further, Japanese Patent Publication No. 3422798 discloses a touch roll that a thin-walled metallic outer cylinder is rotatably attached to an irrotational center support shaft concentrically, while a rubber roll is attached to the center support shaft in the thin-walled metallic outer cylinder, rotatably and eccentrically. In this touch roll, due to its eccentricity, an outer circumferential surface of the rubber roll abuts on an inner circumferential surface of the thin-walled metallic outer cylinder, so that rubber-like elasticity of the rubber roll has charge of an elastic deformation of the thin-walled metallic outer cylinder caused by its pressing load applied on a main roll (i.e. rubber roll's “inner pressure” supporting).
According to a sheet or film-forming roll employing such a “rubber-roll inscribing type” touch roll that performs the rubber roll's inner pressure supporting against the thin-walled metallic outer cylinder, it is possible to form a thin sheet or film in comparison with a sheet or film-forming roll employing a touch roll including a metallic outer cylinder provided with a thin-walled structure only, because the pressing load on the main roll allows the thin-walled metallic outer cylinder to be deformed elastically and appropriately while following the outer circumferential surface of the main roll.
However, in the sheet or film-forming roll employing such a “rubber-roll inscribing type” touch roll disclosed in Japanese Patent Publication No. 3422798, it has to operationally connect the thin-walled metallic outer cylinder with an electric motor in order to rotate the forming roll since the center support shaft is formed by an irrotational shaft. As a result, this makes it difficult to be used for an existing general sheet or film-forming apparatus because its driving system is complicated in structure.